Capacitive touch screen having dynamic capacitance control and improved touch-sensing

ABSTRACT

Methods and apparatus for improving the sensing performance of a capacitive touch screen sensing device. The electrical potential of conductive structures proximate capacitive touch pads of the sensing device is altered to compensate for the effect of parasitic capacitance, based on external conditions such as water on the touch screen or an intervening user worn glove. The compensation for parasitic capacitance improves the signal to noise ratio and therefore the sensing performance of the device.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/377,837, filed Aug. 27, 2010, and entitled CAPACITIVETOUCH SCREEN HAVING DYNAMIC CAPACITANCE CONTROL AND IMPROVEDTOUCH-SENSING, said application being hereby fully incorporated hereinby reference.

FIELD OF THE INVENTION

The invention relates to capacitive touch sensing technologies. Morespecifically, the invention relates to capacitive touch sensing screenssuch as those used in mobile phones and other digital appliances.

BACKGROUND OF THE INVENTION

Touch screens are electronic visual displays that can detect thepresence and location of a touch on the surface of the display area.Touching of the display is generally done with a finger or hand. Touchscreens operate under a variety of electronic, acoustic or opticalprincipals. This application is concerned with capacitive touch screens.

Capacitive touch screen panels generally include an insulator, such asglass, coated with a transparent conductor, such as copper or indium tinoxide (ITO). Because the human body is also a conductor, touching thetouch screen results in a measurable change in capacitance. The changein capacitance caused by the touch is localized and registered to aparticular location on the touch screen.

Capacitive touch sensing technologies including discrete touch pads andmulti-touch screens have recently gained great acceptance in productsranging from cell phones to large display monitors. Many believe thesuccess of these technologies is a direct result of the improved userinteraction as experienced by the users.

One benefit of using a solid state touch sensing technology is itsvirtually unlimited life. Unlike mechanical alternatives which havemoving components that wear with time in repeated use, a solid statetouch sensing screen has no such limitation. Solid state touch sensingscreens rarely fail and users worry little about a broken userinterface. Capacitive touch sensors can be integrated underneath asingle solid sealed surface, such as glass or molded plastic, whichmakes the sensitive components inside the product separated from andlargely immune from the outside environment. This is very difficult andcostly to achieve with mechanical alternatives. Thus, capacitive touchscreen technologies provide great benefits for products that are used inharsh outdoor environments, industrial facilities and other locationsthat are subject to dirt and moisture.

In a typical implementation of a capacitive touch sensing device, thetarget touch sensing pad, which is typically a square, rectangular orcircular area of copper or indium tin oxide (ITO) on a carrier such asglass reinforced epoxy laminate (FR4), printed circuit board (PCB) orpolyethylene terephthalate. (PET). The target touch sensing pad isactively charged then permitted to passively discharge at a rate whichis proportional to its natural capacitance. The rate of discharge of thetarget touch sensing pad is measured using one of several well knownmethods. When a finger or other conductive appendage is placed over thetouch sensing pad, the presence of the finger increases the capacitanceof that pad by adding to the pad's natural capacitance. In this state,the touch sensing pad is able to hold more charge and as a result takeslonger to discharge. By measuring the difference in the time it takes todischarge a particular touch sensing pad in the two states, one candetermine if the pad is being touched or not.

The amount of increase in capacitance when a finger is placed againstthe touch sensing pad varies dependent upon the design and constructionof the touch sensing pad. The greater the capacitive coupling betweenthe finger and the touch sensing pad, the greater the change incapacitance. Conversely, the less the coupling between the finger andthe touch sensing pad the less the change in capacitance due to thetouch. Higher changes in capacitance when the touch sensing pad istouched yield a higher signal to noise ratio (SNR) which translates tobetter performance of the touch sensing pad. The proportion of increasein capacitance of the touch sensing pad when it is touched by a fingeris a function of the natural capacitance of the pad and the addedcapacitance provided by the presence of the finger. Accordingly, if thepad has low natural capacitance coupled with a better coupling to ahuman finger, better sensitively and performance to touch will bedemonstrated.

The natural capacitance of a touch sensing pad is determined by severalfactors. The choice of materials used in construction of the padincluding but not limited to the material of the carrier (which is thedielectric substrate to which the conductive sensor is attached), theprotective substrate (which is the surface behind which the sensor isprotected) and the conductors. The placement of other conductors aroundthe touch sensing pad and the electrical potential on those conductorsalso affects the natural capacitance of the touch sensing pad. Thecoupling between the conductor and the protective substrate also affectsthe natural capacitance of the touch sensing pad. There are many otherfactors and this list should not be considered to be exhaustive.Accordingly, the approach of seeking lower natural capacitance withbetter coupling to a human finger inherently fixes and affects thenatural capacitance of the touch sensing pad. This also limits theability to affect the SNR without completely altering the constructionof the sensor. Altering the construction of the sensor is difficult andexpensive and can even be impossible. The presence of these limitationstends to lead to poorly performing or very expensive solutions.Accordingly, there is room for the improvement in the area ofcapacitance touch sensing screens.

SUMMARY OF THE INVENTION

Embodiments of the present invention involve the selective manipulationof electrical potential, and accordingly, the effect of capacitanceassociated with structures in and around a touch screen or elements ofthe touch screen such as the sensing pads. Embodiments of the presentinvention may include the use of electrically manipulated conductivesurfaces (EMCS). In one embodiment of the invention, EMCS arestrategically placed conductive surfaces that can be electricallymanipulated by, for example, controlling their electrical potential orcharge. EMCS can be purposely applied to affect the capacitance of thetouch sensing pad by changing the electrical potential of the EMCS inways that affect the sensitivity and performance of that touch sensingpad.

In another embodiment of the invention, EMCS can be implemented as othertouch sensing pads that can be electrically manipulated. When this isdone, time multiplexing of a plurality of touch sensing pads as sensorsor EMCS yields similar results and allows precise tuning of the naturalcapacitance of each touch sensing pad. Each conductive pad is chargedand monitored for rate of discharge in a predetermined sequence as touchis sensed. Inactive pads that are not being used for touch sensing andthat are adjacent to the active sensing pad can be used as EMCS bycontrolling their charge level relative to the active sensing pad.Effective use of EMCS enables the ability to adjust the relative chargeand capacitance of the touch sensing pads dynamically and to optimize itfor desired performance.

A typical capacitive touch screen includes a substrate on which anadhesive is applied, a touch pad made from a printed circuit board (PCB)is then adhered to the substrate with the adhesive. Traces, otherconductors, a processor, and other electrical components may be formedon, or attached to, the PCB.

Parasitic capacitance is the unavoidable and usually unwantedcapacitance that exists between the parts of an electronic component orcircuit simply because of the proximity of conductive parts to eachother. All actual circuit elements such as inductors, diodes andtransistors have internal capacitance which can cause their actualbehavior to depart from that of ideal circuit elements. Parasiticcapacitance can also exist between closely spaced conductors such aswires or printed circuit board traces.

A typical touch pad may have a natural capacitance of approximately tenpicofarads (pf). Adjacent traces on the printed circuit board, otherconductive artifacts and the protective substrate, among other things,add parasitic capacitance. The additional parasitic capacitance resultsin a net increase of the overall capacitance of a touch pad beyond thenatural capacitance of the touch pad alone. This concept is depicted inFIG. 3. The increase in overall capacitance caused by parasiticcapacitance can range from a few picofarads (pf) to any practical upperlimit.

A typical example touch pad that is a part of a touch screen may, forexample, be structured as a disk 14 mm in diameter. At this size, thetypical human finger can completely cover the surface area of the touchpad when the finger is placed on the top of the touch pad. This helps tomaximize capacitive coupling between the finger and the touch pad andgenerates a high signal to noise ratio. The increase in capacitanceresulting from the presence of the finger on the touch pad can be asmuch as approximately five pf. Dependent upon the influence of parasiticcapacitance on the touch pad, such a five pf addition in capacitancecaused by the presence of the finger over the touch pad can result in anincrease overall capacitance of 50 percent, assuming a naturalcapacitance of 10 pf. If the magnitude of added parasitic capacitance ishigh, however, the overall capacitance will be increased bysignificantly less than 50 percent. If the parasitic capacitance isexceptionally high, the percentage increase in capacitance created byplacement of the finger over the touch pad can approach zero, in whichcase, the presence of a finger touch cannot be detected. Such a largeincrease in parasitic capacitance can result from, for example, thepresence of water or other conductive substances on the surface of thetouch screen pad.

An example touch screen pad in accordance with the invention, whichincludes EMCS, is depicted in FIG. 4. In this example embodiment, theEMCS disposed around the various touch screen pads is coupled toelectronics by which the electrical potential, and thereby the effectivecapacitance between the EMCS and the touch screen pad can bemanipulated. By adjusting the potential on the EMCS, the alteration ofthe natural capacitance of the touch pad by the presence of a finger canbe manipulated to increase or decrease the effect that the presence ofthe finger has when coupling to the touch pad.

For example, if the natural capacitance of the touch pad isapproximately 10 pf and the parasitic capacitance adds another 10 pf,the presence of the finger over the touch pad adds an additional 5 pf,then the change due to the presence of the finger is an increase of 25%.In accordance with the invention, however, EMCS are used to reduce orcompensate for the parasitic capacitance. When the parasitic capacitanceis reduced and if the natural capacitance and the added capacitance ofthe presence of the finger remain the same, there is a net increase inthe percentage effect of the finger as compared to the sum of thenatural capacitance in the parasitic capacitance, hence, a larger signalto noise ratio (SNR) which leads to better sensing and greater designflexibility in accordance with the invention.

According to embodiments of the invention, changes in the effectiveamount of parasitic capacitance affecting sensing function on a touchscreen can be altered strategically. For example, the amount of nettotal capacitance (natural capacitance plus parasitic capacitance)affecting the sensing function can be uniformly altered according toexpected conditions. For example, if it is expected that water might bepresent on the screen, the electrical potential of the touch sensingelements and the other components that might induce parasiticcapacitance can be equalized, such that the change in overall netcapacitance induced by the presence of a layer of water on the screen isreduced or virtually eliminated. In such cases where the additionalcapacitance induced by the water is reduced, the amount of capacitancechange induced by the finger of a user touching the screen is relativelygreater, thereby improving responsiveness and performance of the touchscreen.

In other cases the amount of capacitance change induced by a user touchmight be expected to be decreased from that which might be expected tobe induced by close proximity of the user's finger with the touchsensor. For example, a glove worn by the user might result in the user'sfinger being disposed further from the touch sensor, thereby decreasingthe amount of additional capacitance the user's finger adds to thesystem. In such cases, it is advantageous to increase the sensitivity ofthe touch screen by reducing the overall capacitance of the touch screen(natural plus parasitic capacitance) thereby increasing the relativeamount of change induced by the user touch and easing detection.

Accordingly, an advantage of certain embodiments of the invention isthat manipulation of effective capacitance enables greater touch screendesign flexibility to account for known external conditions such as thepresence of water on the touch screen or a user wearing thick gloves.

Another advantage of certain embodiments is a touch screen device with ahigher signal to noise ratio, offering improved ability to detect smallchanges in capacitance due to a user touch.

Another advantage of certain embodiments is the ability to dynamicallyadjust sensing performance of the touch pad to compensate for designconstraints or known external conditions.

According to an embodiment of the invention, a method of improving thesensing performance of a capacitive touch screen device including atleast one capacitive touch pad element, the method includes selectivelyaltering a magnitude of an electrical potential of at least oneelectrically conductive structure proximate the at least one capacitivetouch pad element based on an electrical potential of the at least onecapacitive touch pad element, to alter an effective capacitance of theat least one capacitive touch pad element, and subsequently detecting auser touch of the at least one capacitive touch pad element. In anembodiment, the electrical potential of the at least one electricallyconductive structure is altered to substantially match the electricalpotential of the at least one capacitive touch pad element. In analternative embodiment, the electrical potential of the at least oneelectrically conductive structure is altered to a magnitudesubstantially different from the electrical potential of the at leastone capacitive touch pad element. The method may further includedisposing a plurality of electrically conductive elements proximate theat least one capacitive touch pad element. The electrical potential ofeach of the plurality of electrically conductive elements may be alteredbased on the electrical potential of the at least one capacitive touchpad element. In another embodiment, the capacitive touch screen mayincludes a plurality of capacitive touch pad elements, and a pluralityof electrically conductive elements may be disposed proximate eachcapacitive touch pad element of the plurality. The at least oneelectrically conductive element may be another capacitive touch padelement disposed proximate the at least one capacitive touch padelement.

In other embodiments a capacitance touch sensing device includes aplurality of capacitive touch sensing pads operatively coupled with aprocessor for sensing a user touch, at least one electrically conductiveelement disposed proximate each one of the plurality of capacitive touchsensing pads, and apparatus for selectively altering a magnitude of anelectrical potential of the conductive elements based on a magnitude ofan electrical potential of the capacitive touch sensing pads and basedon an expected external condition. The expected external condition maybe the presence of water on the capacitive touch sensing device, and theelectrical potential of the electrically conductive elements may bealtered to substantially match the electrical potential of thecapacitive touch sensing pads. In other embodiments, the expectedexternal condition may be a user glove intervening between a user'sfinger and the capacitive touch sensing pads, and the electricalpotential of the electrically conductive elements may be altered tosubstantially match the electrical potential of the capacitive touchsensing pads.

In an embodiment, the electrically conductive elements may be othercapacitive touch pads of the plurality of capacitive touch pads. Inother embodiments, the electrically conductive elements are conductivestructures separate from the capacitive touch pads. The electricallyconductive elements may be formed on a same substrate as the capacitivetouch pads.

In another embodiment, a method of compensating for parasiticcapacitance in a capacitive touch screen device including at least onecapacitive touch pad element includes selectively altering a magnitudeof an electrical potential of at least one electrically conductivestructure proximate the at least one capacitive touch pad element basedon an electrical potential of the at least one capacitive touch padelement, and subsequently detecting a user touch of the at leastcapacitive touch pad element.

In an embodiment, the electrical potential of the at least oneelectrically conductive structure is altered to substantially match theelectrical potential of the at least one capacitive touch pad element.In another embodiment the electrical potential of the at least oneelectrically conductive structure is altered to a magnitudesubstantially different from the electrical potential of the at leastone capacitive touch pad element. The method may further includedisposing a plurality of electrically conductive elements proximate theat least one capacitive touch pad element. The electrical potential ofeach of the plurality of electrically conductive elements may be alteredbased on the electrical potential of the at least one capacitive touchpad element.

In another embodiment, the capacitive touch screen includes a pluralityof capacitive touch pad elements, and a plurality of electricallyconductive elements is disposed proximate each capacitive touch padelement of the plurality. The at least one electrically conductiveelement may be another capacitive touch pad element disposed proximatethe at least one capacitive touch pad element.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the present invention may be more completelyunderstood in consideration of the following detailed description ofvarious embodiments in connection with the accompanying drawings, inwhich:

FIG. 1 is a schematic plan view of an example touch pad displayaccording to an embodiment of the invention;

FIG. 2 is a schematic elevational view of the example touch pad displayof FIG. 1;

FIG. 3 is a schematic view of an example prior art touch pad displaydepicting the presence and effect of parasitic capacitance;

FIG. 4 is a schematic view of an exemplary touch pad display includingelectrically manipulated conductive surfaces according to an embodimentof the invention;

FIG. 5 is a schematic view of an exemplary touch pad display includingelectrically manipulated conductive surfaces according to an alternativeembodiment of the invention; and

FIG. 6 is a block schematic diagram of a touch pad sensing deviceaccording to an embodiment of the invention.

While the present invention is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the presentinvention to the particular embodiments described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the present invention asexpressed in the appended claims.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, capacitive touch sensing screen device 10generally includes substrate 12, adhesive 14, touch sensing screen 16,PCB substrate 18, traces 20 and a controlling processor in the form ofintegrated circuit 22. Processor 22 or other electronic components arecoupled to traces 20 to control and manipulate the charge on structuresof capacitive touch sensing screen 10 as is known in the art.

Referring now to FIG. 3, a typical prior art capacitive touch sensingscreen 16 includes first touch pad 24, second touch pad 26, third touchpad 28, touch pad conductors 30 coupled to traces 20, metal bracket 32and screw 34. Metal bracket 32 and screw 34 are generally at chassisground potential. Parasitic capacitance 36 is depicted in FIG. 3.Parasitic capacitance 36 exists between various conductive parts of thecircuit because of the proximity of conductive parts to each other. InFIG. 3, parasitic capacitance is depicted as existing between firsttouch pad 24, second touch pad 26 and third touch pad 28 as well asbetween first touch pad 24 and metal bracket 32 between third touch pad28 and screw 34 and between conductors 30. Parasitic capacitance mayalso be added by other elements, such as other conductive artifacts, andthe protective substrate itself.

In the prior art touch screen of FIG. 3, the magnitudes of the parasiticcapacitances 36 are unpredictable. For example, the magnitude of any oneof the parasitic capacitances 36 may range from zero up to 10 pf ormore. Assuming a natural capacitance of the touch pads 24, 26, 28, ofabout 10 pf, the additive effect of the parasitic capacitance might makethe net capacitance of the touch screen 10 as much as 20 pf or more.Assuming a finger touch adds another 5 pf, the total change incapacitance due to a finger touch would be only about 25% (5 pf/20 pf),or possibility even less. As such, the SNR is very low and the usabledetectable range of change in capacitance is limited to about 25%. Thisloss of information limits the ability to sense fine changes incapacitance, such as for example, when the touch pad is used with glovesor when it is wet.

Referring to FIGS. 4 and 6, a first example embodiment of the inventionis depicted in which touch pad 16 includes including electricallymanipulated conductive surfaces (EMCS) 38 according to an embodiment ofthe invention. EMCS elements 38 can be formed from the same material astouch pads 24, 26, 28, for example ITO, or can be any other suitableconductive material. EMCS elements 38 can be formed on the samesubstrate as the touch pads 24, 26, 28, or can be placed on a separateadjacent substrate. EMCS elements 38 are coupled through conductors 41to electrical power supply 50 through potential adjustment apparatus 52.Potential adjustment apparatus 52 may be any suitable known circuitrycapable of altering an output electrical potential applied to conductors41 in response to a signal from processor 22. Alternatively, potentialadjustment apparatus 52 may be omitted and conductors 41 may be coupleddirectly with processor 22, with processor 22 effecting the desiredpotential adjustments.

Manipulated capacitances 40 exist between EMCS 38 and first touch pad24, second touch pad 26 and third touch pad 28 as depicted in FIG. 4. Inaccordance with embodiments of the invention, the electrical potentialapplied to EMCS 38 is manipulated and controlled relative to theelectrical potential of first touch pad 24, second touch pad 26 andthird touch pad 28, thereby manipulating the effective capacitive valueof manipulated capacitances 40. Because the electrical potential appliedto EMCS, and therefore the effective value of manipulated capacitances40, is actively controlled, the sensitivity of first touch pad 24,second touch pad 26 and third touch pad 28 can be adjusted, and theeffect of additional parasitic capacitances, for example, caused bywater on the surface of touch capacitance sensing screen 10 can bemitigated or negated.

Referring now to FIG. 4, in a first example of a strategy for mitigatingthe effect of water on touch screen 10, EMCS elements 38 are set to thesame electrical potential as first touch pad 24, second touch pad 26,and third touch pad 28. For instance, if first touch pad 24, secondtouch pad 26, and third touch pad 28, are operated with a +2.0 VDCpotential, EMCS elements 38 are all charged at the same +2.0 VDCpotential. Since there is no difference in potential between first touchpad 24, second touch pad 26, third touch pad 28, and EMCS elements 38,manipulated capacitances 40 are effectively set to zero. Hence, assumingeach touch pad 24, 26, 28, has a natural capacitance of 10 pf, thereduction of any parasitic capacitance component to effectively zeromakes the net capacitance of touch screen 10 essentially equal to the 10pf natural capacitance of the touch pads 24, 26, 28. Any parasiticcapacitance added by a layer of water on touch screen 10 will not affectsensing performance, since it adds capacitance equally to touch pads 24,26, 28, and EMCS elements 38, and these are all at the same electricalpotential. When a finger touch is made to any of touch pads 24, 26, 28,assuming the finger touch adds 5 pf, the touched pad will appear to havea total capacitance of 15 pf, a 50% increase from its naturalcapacitance of 10 pf. This effectively doubles the SNR from the priorart touch screen without EMCS, even when water is present on touchscreen 10.

A similar strategy can be beneficial when compensating for theattenuation of capacitive coupling due to a user wearing gloves. Theincreased distance of a user's finger from the touch pad because of thethickness of a glove can result in a decreased magnitude of capacitivecoupling between the user's finger and the touch pad. For example, auser's finger touch may result in only a 2 pf increase in netcapacitance of the touch screen when the user is wearing a glove, asopposed to a 5 pf increase when the user touches the screen with a barefinger. In the case of the prior art touch pad of FIG. 3, whereinparasitic capacitances amounting to 10 pf add to the 10 pf naturalcapacitance of the touch pads 24, 26, 28, for a total capacitance of 20pf, the change in capacitance of 2 pf would amount to only a 10%change—an amount of change difficult to distinguish from changes due tonoise.

In the EMCS embodiment of FIG. 4, however, with the electrical potentialof the EMCS elements 38 set to the same electrical potential as thetouch pads 24, 26, 28, thereby eliminating the effect of parasiticcapacitance, each touch pad 24, 26, 28, has an overall capacitance equalto its natural capacitance of 10 pf. In this case, the 2 pf change dueto a user touch through a glove amounts to a 20% change in capacitance,which is much easier to distinguish from changes due to noise.

EMCS can also be beneficially employed in a case where the change incapacitance due to a user touch is actually too large to be effectivelymeasured by the hardware associated with the touch screen. This causessignal clipping—or in other words loss of signal/information. Byapplying an appropriate potential to the EMCS elements 38, it becomespossible to limit the change due to touch while preserving signalintegrity and stability. This makes it possible to reliably infersmaller changes due to the reduced gain and also makes it possible toapply capacitive sensing to a much broader set of products.

Referring again to FIG. 4 and assuming the same natural capacitance oftouch pads 24, 26, 28, of 10 pf, the electrical potential of EMCSelements 38 can be set at one-half the electrical potential of touchpads 24, 26, 28. In an example embodiment, this can result in amanipulated capacitance 40 value of 5 pf, thereby establishing theoverall net capacitance of touch pads 24, 26, 28, at 15 pf. If the addedcapacitance from a user touch is assumed to be 5 pf, then the result isa 25% change in capacitance, which may better accommodate the sensingrange of a processor coupled to the touch pads 24, 26, 28. In a furtherembodiment, these and other such beneficial strategies can beselectively employed dynamically in response to sensed conditions. Forexample, if a signal clipping condition is detected by the processor,the electrical potential of the EMCS elements 38 can be reduced by analgorithm programmed in the processor to a level where signal clippingno longer occurs, but that is still at a level high enough to negate theeffects of parasitic capacitance, thereby optimizing the SNR of thetouch screen.

Similarly, using known methods and apparatus for detecting the presenceof water, an algorithm programmed in the processor can increase theelectrical potential applied to EMCS elements 38 from a level wheremanipulated capacitances 40 are non-zero to a level equal to thepotential of touch pads 24, 26, 28, so as to make manipulatedcapacitances 40 effectively zero. Hence, the effect of water on touchscreen 10 can be effectively addressed dynamically when it occurs.

In another embodiment of the invention depicted in FIG. 5, first touchpad 24, third touch pad 28, and adjacent conductive structures such asmetal bracket 32 and screw 34 can act as EMCS elements, such thatmanipulated capacitances 42 are established. As each touch pad 24, 26,28, is scanned in turn by the processor to detect capacitance change,the electrical potentials of the adjacent touch pads can be adjusted toa desired level, such as described above, so as to affect sensingperformance. For example, when second touch pad 26 is active, theelectrical potentials of first touch pad 24 and third touch pad 28 canbe adjusted to affect the sensitivity of second touch pad 26. In a casewhere water is present on the screen for example, the potentials offirst touch pad 24 and third touch pad 28 can be adjusted to match thepotential of second touch pad 26, thereby making manipulated capacitance42 effectively zero. In addition, if metal bracket 32 and screw 34 areisolated from chassis ground, the same electrical potential can beapplied to these elements as to touch pads 24, 26, 28, through conductor44, thereby making effectively zero the manipulated capacitance 42 dueto these elements. Thus, EMCS can be used to adjust the capacitances oftouch sensing pads dynamically and optimized the capacitances of thetouch sensing pads for desired sensitivity, even where no separatededicated EMCS elements are used.

The foregoing descriptions present numerous specific details thatprovide a thorough understanding of various embodiments of theinvention. It will be apparent to one skilled in the art that variousembodiments, having been disclosed herein, may be practiced without someor all of these specific details. In other instances, components as areknown to those of ordinary skill in the art have not been described indetail herein in order to avoid unnecessarily obscuring the presentinvention. It is to be understood that even though numerouscharacteristics and advantages of various embodiments are set forth inthe foregoing description, together with details of the structure andfunction of various embodiments, this disclosure is illustrative only.Other embodiments may be constructed that nevertheless employ theprinciples and spirit of the present invention. Accordingly, thisapplication is intended to cover any adaptations or variations of theinvention.

1. A method of improving the sensing performance of a capacitive touchscreen device including at least one capacitive touch pad element, themethod comprising: selectively altering a magnitude of an electricalpotential of at least one electrically conductive structure proximatethe at least one capacitive touch pad element based on an electricalpotential of the at least one capacitive touch pad element, to alter aneffective capacitance of the at least one capacitive touch pad element;and subsequently detecting a user touch of the at least capacitive touchpad element.
 2. The method of claim 1, wherein the electrical potentialof the at least one electrically conductive structure is altered tosubstantially match the electrical potential of the at least onecapacitive touch pad element.
 3. The method of claim 1, wherein theelectrical potential of the at least one electrically conductivestructure is altered to a magnitude substantially different from theelectrical potential of the at least one capacitive touch pad element.4. The method of claim 1, further comprising disposing a plurality ofelectrically conductive elements proximate the at least one capacitivetouch pad element.
 5. The method of claim 4, wherein an electricalpotential of each of the plurality of electrically conductive elementsis altered based on the electrical potential of the at least onecapacitive touch pad element.
 6. The method of claim 1, wherein thecapacitive touch screen includes a plurality of capacitive touch padelements, and wherein a plurality of electrically conductive elements isdisposed proximate each capacitive touch pad element of the plurality.7. The method of claim 1, wherein the at least one electricallyconductive element is another capacitive touch pad element disposedproximate the at least one capacitive touch pad element.
 8. Acapacitance touch sensing device, comprising: a plurality of capacitivetouch sensing pads operatively coupled with a processor for sensing auser touch; at least one electrically conductive element disposedproximate each one of the plurality of capacitive touch sensing pads;and apparatus for selectively altering a magnitude of an electricalpotential of the conductive elements based on a magnitude of anelectrical potential of the capacitive touch sensing pads and based onan expected external condition.
 9. The capacitive touch sensing deviceof claim 8, wherein the expected external condition is the presence ofwater on the capacitive touch sensing device, and wherein the electricalpotential of the electrically conductive elements is altered tosubstantially match the electrical potential of the capacitive touchsensing pads.
 10. The capacitive touch screen device of claim 8, whereinthe expected external condition is a user glove intervening between auser's finger and the capacitive touch sensing pads, and wherein theelectrical potential of the electrically conductive elements is alteredto substantially match the electrical potential of the capacitive touchsensing pads.
 11. The capacitive touch screen sensing device of claim 8,wherein the electrically conductive elements are other capacitive touchpads of the plurality of capacitive touch pads.
 12. The capacitive touchscreen sensing device of claim 8, wherein the electrically conductiveelements are conductive structures separate from the capacitive touchpads.
 13. The capacitive touch screen sensing device of claim 12,wherein the electrically conductive elements are formed on a samesubstrate as the capacitive touch pads.
 14. A method of compensating forparasitic capacitance in a capacitive touch screen device including atleast one capacitive touch pad element, the method comprising:selectively altering a magnitude of an electrical potential of at leastone electrically conductive structure proximate the at least onecapacitive touch pad element based on an electrical potential of the atleast one capacitive touch pad element; and subsequently detecting auser touch of the at least capacitive touch pad element.
 15. The methodof claim 14, wherein the electrical potential of the at least oneelectrically conductive structure is altered to substantially match theelectrical potential of the at least one capacitive touch pad element.16. The method of claim 14, wherein the electrical potential of the atleast one electrically conductive structure is altered to a magnitudesubstantially different from the electrical potential of the at leastone capacitive touch pad element.
 17. The method of claim 14, furthercomprising disposing a plurality of electrically conductive elementsproximate the at least one capacitive touch pad element.
 18. The methodof claim 17, wherein an electrical potential of each of the plurality ofelectrically conductive elements is altered based on the electricalpotential of the at least one capacitive touch pad element.
 19. Themethod of claim 14, wherein the capacitive touch screen includes aplurality of capacitive touch pad elements, and wherein a plurality ofelectrically conductive elements is disposed proximate each capacitivetouch pad element of the plurality.
 20. The method of claim 14, whereinthe at least one electrically conductive element is another capacitivetouch pad element disposed proximate the at least one capacitive touchpad element.